It's not like Google was ever going to be a showcase customer for Microsoft, but a report that the search giant is phasing out Microsoft Windows underscores security concerns that have long dogged the widely-used software.

According to a report in the Financial Times, Google (NASDAQ: GOOG) began moving employees to other operating systems back in January after its systems were hacked by what the company said were operatives working out of China, a charge corroborated by Internet infrastructure provider VeriSign .

Google was one of at least two dozen U.S. businesses targeted in the attacks that security firm McAfee (NYSE: MFE) said exploited a flaw in Microsoft's Internet Explorer browser. Google has long been a strong supporter of Linux, and the FT report said employees are being moved to Linux and Apple's Mac OS.

But in a blog post Tuesday, McAfee said the success of the attacks owed more to the intelligence gathered by the hackers about their targets than the specific technology that was compromised.

"They knew what their victims were running and what their roles were. The attackers even knew what application versions they used," David Marcus, security research and communications manager at McAfee Avert Labs, said in the blog.

"Would it make any difference if the victims were running Linux or any other operating system if an attacker builds such a sophisticated profile? Not remotely," Marcus added. "Linux, Windows, Mac, whatever -- everything has weaknesses. Especially the users of those systems."

Google did not confirm or deny a change in policy. "We're always working to improve the efficiency of our business, but we don't comment on specific operational matters," the company said in an e-mail to InternetNews.com

A Microsoft (NASDAQ: MSFT) spokesperson said the company had no comment on the report.

Google is working on its own Chrome operating system that's due out this fall. The Chrome OS is designed for a new generation of portable computers running Web services.

The company is also known to test new services internally and encourage staff to use its own products whenever possible so a move away from Windows is not a huge stretch. However, Google, which has more than 10,000 employees worldwide, has traditionally been flexible about allowing a choice of software including Windows.

The Financial Times cited several unnamed Google employees describing the change in OS policy at Google, which includes giving new employees the option of using Apple's Mac computers or PCs running Linux.

For now, there is apparently nothing like a total ban on Windows. Google staffers who want to stay on Windows require clearance from "quite senior levels," a Google employee told the Times. "Getting a new Windows machine now requires CIO approval," said another.

Analyst Charles King said the move away from Windows "makes perfect sense" for a company like Google that's been promoting its own cloud services as an alternative to Windows apps.

"In a sense these are two companies with starkly different visions of what the future of computing will look like," King, principal analyst at Pund-IT, told InternetNews.com. "From a competitive standpoint it makes perfect sense for Google to embrace its own alternative solutions and just step away from the company that's becoming its biggest competitor."

David Needle is the West Coast bureau chief at InternetNews.com, the news service of Internet.com, the network for technology professionals.